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采用差示扫描量热仪(DSC)、扫描电镜(SEM)和X射线衍射仪(XRD)研究了添加钨对钛镍形状记忆合金显微组织与相变行为的影响。研究结果表明,TiNiW_(0.3)和TiNiW_(0.5)(原子分数)合金组成相为母相B2和析出相Ti_2(Ni,W);TiNiW_3和TiNiW_6(原子分数)合金组成相为母相B2、析出相Ti_2(Ni,W)以及富W固溶体相W-s,其中,Ti_2(Ni,W)相扫描电子形貌呈现不规则颗粒状,长条状以及栅栏状,W-s相电子形貌呈现不均匀颗粒状,团簇长大且均匀弥散分布于基体中;同时,添加钨使铸锭晶粒细化,产生了细晶强化与固溶强化效应,屈服强度和硬度随钨含量的增加而提高。850℃保温15min固溶处理后,TiNiW合金冷却/加热过程的相变类型为A→M/M→A,且随钨含量的增加,相变温度范围逐渐宽化,相变温度下降,且降低速率逐渐趋缓。
The effects of tungsten addition on microstructure and phase transition behavior of Ti-Ni shape memory alloy were studied by differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD) The results show that the compositional phases of TiNiW_ (0.3) and TiNiW_ (0.5) (atomic fraction) alloys are B2 and Ti_2 (Ni, W). The composition of TiNiW_3 and TiNiW_6 (atomic fraction) Phase Ti_2 (Ni, W) and W-rich solid solution phase Ws, in which the scanning electron morphology of Ti_2 (Ni, W) phase showed irregular granular, elongated and palisading morphology, Ws phase electronic morphology showed uneven granular , And the clusters grow and disperse uniformly in the matrix. At the same time, the addition of tungsten makes the ingot grain refinement, resulting in the effect of fine grain strengthening and solid solution strengthening. The yield strength and hardness increase with the increase of tungsten content. After the solution heat treatment at 850 ℃ for 15min, the phase transformation type of TiNiW alloy is A → M / M → A. With the increase of tungsten content, the transformation temperature range is gradually broadened and the phase transition temperature is decreased and decreased Slower rate.